Summary auto-generated
This study characterized 200 Vibrio cholerae isolates collected from various provinces in Iran during 1999-2000 using molecular and phenotypic methods. The isolates comprised 171 (86%) V. cholerae O1 biotype El Tor, predominantly Ogawa serotype, and 29 (14%) non-O1, non-O139 strains. Molecular analysis revealed that 33-96% of isolates carried large plasmids (~100 kb), and PCR detection of virulence genes showed tcp, ctx, ace, and zot genes were present in 55-97% of O1 isolates across different provinces. Most O1 strains exhibited significant resistance to trimethoprim/sulfamethoxazole and streptomycin, with some additional resistance to furazolidone and oxytetracycline. Ribotyping identified three distinct patterns in O1 isolates, with pattern B21 predominating in 81% of cases. Non-O1, non-O139 strains showed a single ribotype pattern. Pulsed-field gel electrophoresis (PFGE) identified 10 different patterns overall. The findings indicate that Iranian cholera cases were caused by a limited number of clones, with evidence of genetic diversity and horizontal transfer of antibiotic resistance genes via conjugative plasmids or transposons.
Key findings
- V. cholerae O1 El Tor biotype dominated Iranian isolates (86%), with most showing the B21 ribotype pattern, representing new clones not previously documented in Iran
- Multiple antibiotic resistance was common in O1 strains, with resistance to trimethoprim/sulfamethoxazole and streptomycin transferable via conjugative plasmids or transposons to E. coli recipients
- Virulence genes (ctx, tcp, ace, zot) varied in presence among O1 isolates (55-97% range), while non-O1, non-O139 strains rarely carried these toxin genes
- PFGE analysis identified 10 distinct patterns with greater biodiversity in O1 strains, indicating ongoing genetic diversity and evolution of V. cholerae in Iran
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Abstract
Vibrio cholerae is again the subject of attention on account of the current increase in the world-wide incidence of cholera. In this study, 200 clinical isolates of V. cholerae serotypes O1 and non-O1, non-O139, were collected from different provinces in Iran. The isolates were subjected to biochemical analysis, antibiogram, PCR of toxin genes, plasmid profile, ribotyping and pulsed-field gel electrophoresis (PFGE). The analysis of plasmid content showed that 3396% of V. cholerae isolated from different provinces carry a large plasmid. PCR analysis of V. cholerae O1 showed that the genes encoding cholera toxin (ctx), toxin co-regulated pilus (tcp), accessory cholera enterotoxin (ace) and zonula occludens toxin (zot) were present in 5597% of isolates in different provinces. Restriction fragment length polymorphism (RFLP) of BglI-digested DNA probed with five oligonucleotides revealed three different ribotype patterns in isolates of V. cholerae O1. The ribotype pattern B21 of V. cholerae O1 El Tor was found to be the predominant pattern in the isolates studied. V. cholerae non-O1, non-O139 isolates showed a single ribotype pattern. PFGE analysis also showed 10 different patterns amongst the isolates, 9 of which were in V. cholerae O1. Overall, the analysis of polymorphism of ribotypes and PFGE patterns of the isolates showed that the provinces in Iran were affected by a limited number of clones of V. cholerae O1 and non-O1, non-O139 strains.